Electrostatic spray modules have been used for applying agricultural liquids such as a pesticide to crops where, externally to the spray module the number of connections is reduced to three, one for the liquid pesticide, one for compressed air and one for a low voltage signal. Internally to the spray module, a low voltage is converted to a high voltage signal, which is, along with the pesticide and the compressed air delivered to one or more electrostatic spray nozzles using only two electrically conductive pipes, a gas delivery pipe and a liquid delivery pipe. The nozzles fit into the gas delivery pipe and draw the compressed air through gas channel openings in the side of the nozzles.
In prior art, the gas delivery pipe doubles as the means to deliver the high voltage signal to the nozzles. Each nozzle has a liquid feed from the liquid delivery pipe, which carries ground voltage, maintaining the liquid at ground voltage. The grounded liquid merges with the compressed air in the nozzles to form an atomized liquid. The atomized liquid then passes through an electrode, which is electrically charged by the high voltage signal to form an electrostatic spray. The electrical charge in the spray leads to better dispersal of the spray due to the droplets in the spray repelling from each other, and further improves the adherence of the spray to crops which attract the charged droplets. Examples of the prior art are shown in U.S. Pat. Nos. 6,003,794 and 6,138,922 and 6,227,466 each of which is incorporated herein by this reference.
The prior systems suffer various problems and limitations. First, there is high-voltage current leakage that often occurs where nozzles extend through the shell or casing that encloses the sprayer. Further, the orifice sizes of the nozzles are difficult to change for different applications without tools. Also, the high-voltage power supply may not provide an optimal high-voltage level for some applications. Further, there are challenges and lost time spent in repairing and reconfiguring sprayer systems for different applications. Various improvements to electrostatic spraying equipment and control are disclosed in the description that follows.